MATLAB: How to compute the local curvature of a point given a set of X-Y points in MATLAB 7.9 (R2009b)

MATLAB

I want to compute the local curvature of each point given a set of points that define a two-dimensional curve.

Best Answer

The ability to compute the local curvature at a point given a two-dimensional curve does not come built-in with MATLAB.

As a workaround, refer the following submissions on MATLAB Central that compute the local curvature of an arbitrary surface:

 <http://www.mathworks.com/matlabcentral/fileexchange/11168-surface-curvature>
 <http://www.mathworks.com/matlabcentral/fileexchange/10010-mean-curvature-fast-code>

Note that MathWorks does not guarantee or warrant the use or content of these submissions. Any questions, issues, or complaints should be directed to the contributing author.

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MATLAB: How to obtain the coordinates of the mouse on the screen displayed somewhere in the figure window

This enhancement has been incorporated in MATLAB 7.5 (R2007b).

As a workaround in previous MATLAB releases, you can use the following MATLAB function to track mouse motion:

function mousetrk
%MOUSETRK function to track mouse motion
% This function creates two static text controls
% which contain the x & y coordinates of the mouse
% The driving callback is executed by the
% WindowButtonMotionFcn of the figure.
figure
axes('Visible','off')
xbox = uicontrol('Style','text','Tag','xbox');
xboxlabel = uicontrol('Style','text','String','X Value',...
    'Position',get(xbox,'position')+[0 21 0 0]);
ybox = uicontrol('Style','text','Position',[90 20 60 20],'Tag','ybox');
yboxlabel = uicontrol('Style','text','String','Y Value',...
    'Position',get(ybox,'position')+[0 21 0 0]);
callback = ['pt = get(gca,''CurrentPoint'');'...
  'xbox = findobj(''Tag'',''xbox'');' ...
  'ybox = findobj(''Tag'',''ybox'');' ...
  'set(xbox,''String'',num2str(pt(1,1)));' ...
  'set(ybox,''String'',num2str(pt(1,2)));'];
set(gcf,'WindowButtonMotionFcn',callback);

For more information on the WindowButton functions, please refer to the Handle Graphics Property Browser:

https://www.mathworks.com/help/releases/R2009b/techdoc/infotool/hgprop/doc_frame.html

MATLAB: How to display the progress of a ‘parfor’ or ‘parfeval’ loop in MATLAB R2017a and newer

Building a 'waitbar' during a 'parfor' loop

1, The status of a 'parfor' loop can be displayed during execution using a data queue. The 'parallel.pool.DataQueue' function was added in MATLAB R2017a in order to send data from a MATLAB parallel worker to the MATLAB Desktop client:

https://www.mathworks.com/help/releases/R2017a/distcomp/parallel.pool.dataqueue.html

In particular, the functionality of 'parallel.pool.DataQueue' can be used to display a 'waitbar' on the MATLAB Desktop client while a 'parfor' loop is executing on the parallel workers. Please refer to the following example in the 'parallel.pool.DataQueue' documentation page for more information:

https://www.mathworks.com/help/releases/R2017a/distcomp/parallel.pool.dataqueue.html#bvo5uvj-1

The above example builds a 'parallel.pool.DataQueue' object in the MATLAB client and workers. Then, the 'afterEach' function is used to register a callback function which gets executed on the MATLAB Desktop client whenever new data is available in the queue. Finally, the 'send' function is used within the 'parfor' loop to provide data to the 'parallel.pool.DataQueue'.

Building a 'waitbar' during 'parfeval' execution

The following documentation page provides an example of using the 'waitbar' function to display the progress of a 'parfeval' computation:

https://www.mathworks.com/help/releases/R2016b/distcomp/examples/parfeval-blackjack.html

This example can be opened in MATLAB using:

>> openExample('distcomp/paralleldemo_blackjack_parfeval')

In the above example, note that the 'waitbar' is created and updated on the MATLAB Desktop client, while the computations are running on the MATLAB parallel workers. At the start of the code, 100 'parfeval' computations are queued. The 'waitbar' and plots are updated as each 'parfeval' computation is completed.

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Related Solutions

MATLAB: How to obtain the coordinates of the mouse on the screen displayed somewhere in the figure window

MATLAB: How to display the progress of a ‘parfor’ or ‘parfeval’ loop in MATLAB R2017a and newer

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